1. Field of the Invention
The present invention disclosed in this specification relates to an electronic circuit, a semiconductor device, and an electronic device.
2. Description of the Related Art
In recent years, large scale integration (LSI) chips incorporated into electronic devices such as mobile phones and laptops are required to have a smaller size and a higher data transmission rate. It is suggested to use an electronic circuit which performs wireless communication with the use of a combination of a coil and a semiconductor element such as an LSI chip, utilizing electromagnetic induction, in order to achieve a smaller size and a higher data transmission rate (Patent Document 1). For example, an LSI chip or an electronic device can intercommunicate with an LSI chip. It is expected that the technique is applied to a stacking technique of LSI chips, IC chips, and the like.
In a conventional technique, IC chips have transmitted/received a signal to/from each other through wires which are provided by wire bonding or the like. Further, in recent years, a technique is proposed in which a communication path (referred to as a through hole) penetrating an IC chip is formed. However, the above techniques need an advanced wiring connection step, resulting in high cost; therefore, there is a physical limit on manufacturing stacked IC chips.
On the other hand, stacked IC chips which wirelessly transmit/receive a signal to/from each other have advantages as follows: the yield of the stacked IC chips cannot be lower than the yield of each of the IC chips and integration circuit can be enlarged smoothly without complicated steps (Non Patent Document 1).
The configuration and operation of a conventional receiving circuit which is used for such wireless communication is described with reference to FIG. 11 and FIGS. 12A to 12C. FIG. 11 is a circuit diagram showing an example of the configuration of the conventional receiving circuit and part of a transmitting circuit. FIGS. 12A to 12C are examples of timing diagrams at the time of transmission/reception of signals.
A transmitting circuit 10 includes a coil 11. One of terminals of the coil 11 is connected to a ground potential line. A transmitting rectangular wave signal (TXDATA) is input to the other of the terminals of the coil 11. On the other hand, a receiving circuit 20 includes a coil 21, a first comparator 23a, a second comparator 23b, and a latch circuit 25 including a NAND circuit element. One of terminals of the coil 21 is connected to the ground potential line. The other of the terminals of the coil 21 is connected to an inversion input terminal (hereinafter, also referred to as a − terminal) of the first comparator 23a and a non-inversion input terminal (hereinafter, also referred to as a + terminal) of the second comparator 23b. A first reference voltage (VH) and a second reference voltage (VL) are input to a + terminal of the first comparator 23a and a − terminal of the second comparator 23b, respectively. A voltage higher than 0 V and a voltage lower than 0 V are used for the first reference voltage (VH) and the second reference voltage (VL), respectively. An output terminal of the first comparator 23a and an output terminal of the second comparator 23b are each connected to the latch circuit 25. A first receiving rectangular wave signal (RXDATA) is output from the latch circuit 25. Further, at the same time, a second receiving rectangular wave signal (/RXDATA), which is an inverted output signal of the first receiving rectangular wave signal (RXDATA), is output from the latch circuit 25.
Here, in order to show a positional relation between the coil 11 of the transmitting circuit 10 and the coil 21 of the receiving circuit 20, a black dot is written beside one of terminals of each coil illustrated in FIG. 11. Specifically, in the case of positive coupling coefficient, the direction of current which flows through the coil 11 and the direction of current which flows through the coil 21 are the same with respect to each one of the terminals beside which the black dot is written. Note that coupling coefficient between the coils is positive.
Next, a receiving operation is described with reference to timing diagrams of FIGS. 12A to 12C in addition to FIG. 11. FIG. 12A, FIG. 12B, and FIG. 12C show changes over time in voltages of the transmitting rectangular wave signal (TXDATA), a potential difference (an induced electromotive force VR) between both ends of the coil 21, and the first receiving rectangular signal (RXDATA), respectively. Here, the induced electromotive force (VR) is equal to a voltage input to a − terminal of the first comparator 23a and a + terminal of the second comparator 23b. In the coil 21 shown in FIG. 11, the side beside which the black dot is written is a positive side and the side beside which no black dot is written is a negative side.
When the transmitting rectangular wave signal (TXDATA) changes between a High-level voltage and the Low-level voltage, the induced electromotive force (VR) is generated in the coil 21 by electromagnetic induction; accordingly, a pulsed voltage waveform as shown in FIG. 12B is obtained. When the induced electromotive force (VR) becomes higher than the first reference voltage (VH) input to the first comparator 23a, the High-level voltage is output as the first receiving rectangular wave signal (RXDATA) which is the output voltage of the latch circuit 25. On the other hand, when the induced electromotive force (VR) becomes lower than the second reference voltage (VL) input to the second comparator 23b, the first receiving rectangular wave signal (RXDATA) is inverted and then the Low-level voltage is output. The latch circuit 25 holds the output voltage until the voltage of the transmitting rectangular wave signal (TXDATA) changes.
With the above-described configuration and by the above-described driving method, the receiving circuit 20 receives the transmitting rectangular wave signal (TXDATA) from the transmitting circuit 10 and can restore the transmitting rectangular wave signal (TXDATA) as the first receiving rectangular wave signal (RXDATA).